The present invention is directed to crosslinked fluorosilicone materials. More specifically, the present invention is directed to thermally stabilized crosslinked fluorosilicone materials suitable for applications such as fuser member coatings for imaging processes and the like. One embodiment of the present invention is directed to a fuser member comprising a substrate and at least one layer thereover, said layer comprising a crosslinked product of a liquid composition which comprises (a) a fluorosilicone, (b) a crosslinking agent, and (c) a thermal stabilizing agent comprising a reaction product of (i) a cyclic unsaturated-alkyl-group-substituted polyorganosiloxane, (ii) a linear unsaturated-alkyl-group-substituted polyorganosiloxane, and (iii) a metal acetylacetonate or metal oxalate compound.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member, and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles and pigment particles, or toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support, which can be the photosensitive member itself, or some other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known. To fuse electroscopic toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner to be bonded firmly to the support.
Typically, the thermoplastic resin particles are fused to the substrate by heating to a temperature of from about 90.degree. C. to about 200.degree. C. or higher, depending on the softening range of the particular resin used in the toner. It may be undesirable, however, to increase the temperature of the substrate substantially higher than about 250.degree. C. because of the tendency of the substrate to discolor or convert into fire at such elevated temperatures, particularly when the substrate is paper.
Several approaches to thermal fusing of electroscopic toner images have been described. These methods include providing the application of heat and pressure substantially concurrently by various means, a roll pair maintained in pressure contact a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat can be applied by heating one or both of the rolls, plate members, or belt members. Fusing of the toner particles occurs when the proper combination of heat, pressure, and/or contact for the optimum time period are provided. The balancing of these variables to bring about the fusing of the toner particles is well known in the art, and can be adjusted to suit particular machines or process conditions.
During the operation of one fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between a pair of rolls, plates, belts, or combination thereof. The concurrent transfer of heat and the application of pressure in the nip effects the fusing of the toner image onto the support. It is important in the fusing process that minimal or no offset of the toner particles from the support to the fuser member takes place during normal operations. Toner particles offset onto the fuser member can subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thereby increasing the image background, causing inadequate copy quality, causing inferior marks on the copy, or otherwise interfering with the material being copied there as well as causing toner contamination of other parts of the machine. The referred to "hot offset" occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release properties of the fuser member, and accordingly it is desirable to provide a fusing surface having a low surface energy to provide the necessary release.
To ensure and maintain good release properties of the fuser member, it has become customary to apply release agents to the fuser member during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils, such as polydimethyl siloxane, or substituted silicone oils, such as amino-substituted oils, mercapto-substituted oils, or the like, to prevent toner offset. In addition, fillers can be added to the outer layers of fuser members to increase the bonding of the fuser oil to the surface of the fuser member, thereby imparting improved release properties.
The use of polymeric release agents having functional groups which interact with a fuser member to form a thermally stable, renewable self-cleaning layer having good release properties for electroscopic thermoplastic resin toners, is described in, for example, U.S. Pat. No. 4,029,827, U.S. Pat. No. 4,101,686, and U.S. Pat. No. 4,185,140, the disclosures of each of which are totally incorporated herein by reference. Disclosed in U.S. Pat. No. 4,029,827 is the use of polyorganosiloxanes having mercapto functionality as release agents. U.S. Pat. No. 4,101,686 and U.S. Pat. No. 4,185,140 are directed to polymeric release agents having functional groups such as carboxy, hydroxy, epoxy, amino, isocyanate, thioether, and mercapto groups as release fluids.
It is important to select the correct combination of fuser surface material, any filler incorporated or contained therein, and fuser oil. Specifically, it is important that the outer layer of the fuser member react sufficiently with the selected fuser oil to obtain sufficient release. To improve the bonding of fuser oils with the outer surface of the fuser member, fillers have been incorporated into or added to the outer surface layer of the fuser members. The use of a filler can aid in decreasing the amount of fusing oil necessary by promoting sufficient bonding of the fuser oil to the outer surface layer of the fusing member. It is important, however, that the filler not degrade the physical properties of the outer layer of the fuser member, and it is also important that the filler not cause too much of an increase in the surface energy of the outer layer.
Fillers are also sometimes added to the outer layers of fuser members to increase the thermal conductivity thereof. Examples of such fillers include conductive carbon, carbon black, graphite, aluminum oxide, titanium, and the like, as well as mixtures thereof. Efforts have been made to decrease the use of energy by providing a fuser member which has excellent thermal conductivity, thereby reducing the temperature needed to promote fusion of toner to paper. This increase in thermal conductivity also allows for increased speed of the fusing process by reducing the amount of time needed to heat the fuser member sufficiently to promote fusing. Efforts have also been made to increase the toughness of the fuser member layers to increase abrasion resistance and, accordingly, the life of the fuser member.
With regard to known fuser coatings, silicone rubber has been the preferred outer layer for fuser members in electrostatographic machines. Silicone rubbers interact well with various types of fuser release agents. Perfluoroalkoxypolytetrafluoroethylene (PFA Teflon), however, which is frequently used as an outer coating for fuser members, is more durable and abrasion resistant than silicone rubber coatings. Also, the surface energy for PFA Teflon is lower than that of silicone rubber coatings.
U.S. Pat. No. 5,864,740 (Heeks et al.), the disclosure of which is totally incorporated herein by reference, discloses a thermally stabilized silicone liquid composition and a toner fusing system using the thermally stabilized silicone liquid as a release agent, wherein the thermally stabilized silicone liquid contains a silicone liquid and a thermal stabilizer composition (including a reaction product from at least a polyorganosiloxane and a platinum metal compound (Group VIII compound) such as a ruthenium compound, excluding platinum.
U.S. Pat. No. 5,493,376 (Heeks), the disclosure of which is totally incorporated herein by reference, discloses a thermally stabilized polyorganosiloxane oil including a polyorganosiloxane oil and, as the thermal stabilizer, the reaction product of chloroplatinic acid and a member selected from the group consisting of a cyclic polyorganosiloxane having the formula ##STR1## where R.sub.3 is an alkyl radical having 1 to 6 carbon atoms and R.sub.4 is selected from the group consisting of alkene and alkyne radicals having 2 to 8 carbon atoms, and n is from 3 to 6; a linear polyorganosiloxane having the formula ##STR2## wherein R.sub.1 and R.sub.2 are selected from the group consisting of hydroxy and alkyl, alkoxy, alkene, and alkyne radicals having 1 to 10 carbon atoms, provided that at least one of R.sub.1 and R.sub.2 is alkene or alkyne, and m is from 0 to 50; and mixtures thereof, present in an amount to provide at least 5 parts per million of platinum in said oil.
U.S. Pat. No. 5,395,725 (Bluett et al.), the disclosure of which is totally incorporated herein by reference, discloses a process for fusing toner images to a substrate which comprises providing a fusing member having a fusing surface; heating the fuser member to an elevated temperature to fuse toner to the substrate; and applying directly to the fusing surface a fuser release agent oil blend composition; wherein volatile emissions arising from the fuser release agent oil blend are minimized or eliminated.
U.S. Pat. No. 4,150,181 (Smith), the disclosure of which is totally incorporated herein by reference, discloses a contact fuser assembly and method for preventing toner offset on a heated fuser member in an electrostatic reproducing apparatus which includes a base member coated with a solid, abrasion resistant material such as polyimide, poly(amide-imides), poly(imide-esters), polysulfones, and aromatic polyamides. The fuser member is coated with a thin layer of polysiloxane fluid containing low molecular weight fluorocarbon. Toner offset on the heated fuser member is prevented by applying the polysiloxane fluid containing fluorocarbon to the solid, abrasion resistant surface of the fuser member.
U.S. Pat. No. 3,002,927 (Awe et al.), the disclosure of which is totally incorporated herein by reference, discloses organosilicon fluids capable of withstanding high temperatures which are prepared by preoxygenating the fluid by heating a mixture of (1) a polysiloxane fluid in which the siloxane units are selected from the group consisting of units of the formula R.sub.3 SiO.sub.0.5, R.sub.2 SiO, RSiO.sub.1.5, and SiO.sub.2 in which each R is selected from the group consisting of methyl, phenyl, chlorophenyl, fluorophenyl, and bromophenyl radicals, (2) a ferric salt of a carboxylic acid having from 4 to 18 carbon atoms in an amount such that there is from 0.005 to 0.03 percent by weight iron based on the weight of (1), and (3) oxygen mechanically dispersed in the fluid at a temperature above 400.degree. F. until the mixture changes to a reddish brown color and until the mixture will not form a precipitate when heated in the absence of oxygen at a temperature above that at which the preoxygenation step is carried out.
U.S. Pat. No. 4,711,818 (Henry), the disclosure of which is totally incorporated herein by reference, discloses a thermally conductive dry release fuser member and fusing method for use in electrostatic reproducing machines without the application of a release agent. The fuser member comprises a base support member and a thin deformable layer of a composition coated thereon, the composition comprising the crosslinked product of a mixture of at least one addition curable vinyl terminated or vinyl pendant polyfluoroorganosiloxane, filler, heat stabilizer, a crosslinking agent, and a crosslinking catalyst.
U.S. Pat. No. 5,464,703 (Ferrar et al.) and U.S. Pat. No. 5,563,202 (Ferrar et al.), the disclosures of each of which are totally incorporated herein by reference, disclose a fuser member useful for heat fixing an electrographic toner to a substrate, a composition of matter, and its preparation method. The fuser member has a core and a base cushion layer overlying the core. The base cushion layer includes a crosslinked poly(dimethylsiloxane-fluoroalkylsiloxane) elastomer that has tin oxide particles dispersed therein in a concentration of from 20 to 40 percent of the total volume of the base cushion layer.
Copending Application U.S. Ser. No. 09/375,968, filed concurrently herewith, entitled "Thermally Stable Silicone Fluids," with the named inventors George J. Heeks, David J. Gervasi, Arnold W. Henry, and Santokh S. Badesha, the disclosure of which is totally incorporated herein by reference, discloses a fuser release agent comprising (a) a polyorganosiloxane, and (b) a stabilizing agent comprising the reaction product of (i) a metal acetylacetonate or metal oxalate compound, (ii) a linear unsaturated-alkyl-group-substituted polyorganosiloxane, and (iii) a cyclic unsaturated-alkyl-group-substituted polyorganosiloxane.
Copending Application U.S. Ser. No. 09/375,592, filed concurrently herewith, entitled "Stabilized Fluorosilicone Materials," with the named inventors George J. Heeks, David J. Gervasi, Arnold W. Henry, and Santokh S. Badesha, the disclosure of which is totally incorporated herein by reference, discloses a composition comprising a crosslinked product of a liquid composition which comprises (a) a fluorosilicone, (b) a crosslinking agent, and (c) a thermal stabilizing agent comprising a reaction product of (i) a cyclic unsaturated-alkyl-group-substituted polyorganosiloxane, (ii) a linear unsaturated-alkyl-group-substituted polyorganosiloxane, and (ii) a metal acetylacetonate or metal oxalate compound.
Copending Application U.S. Ser. No., 09/325,974, filed concurrently herewith, entitled "Stabilized Fluorosilicone Transfer Member," with the named inventors George J. Heeks, David J. Gervasi, Arnold W. Henry, and Santokh S. Badesha, the disclosure of which is totally incorporated herein by reference, discloses a transfer member comprising a crosslinked product of a liquid composition which comprises (a) a fluorosilicone, (b) a crosslinking agent, and (c) a thermal stabilizing agent comprising a reaction product of (i) a cyclic unsaturated-alkyl-group-substituted polyorganosiloxane, (ii) a linear unsaturated-alkyl-group-substituted polyorganosiloxane, and (iii) a metal acetylacetonate or metal oxalate compound, said transfer member having surface a resistivity of from about 10.sup.4 to about 10.sup.16 ohms per square.
Silicone rubbers are widely used in fusing subsystems, largely because they can be modified to optimum fusing properties. Desirable physical properties in fusing materials include thermal conductivity, hardness, and toughness. One disadvantage of using silicone rubbers is that silicone rubbers swell in various solvents and in silicone oils. In current release agent technology, silicone oils are commonly used, but because of the swelling of silicone rubber in the oil, it is often necessary to coat the silicone fuser rolls with a fluoropolymer. Fluorosilicones that will resist swelling and possess the preferred physical properties for fusing are also available, but fluorosilicones are unstable at high temperatures (for example, over 300.degree. F.), and they can release trifluoropropionaldehyde, an acute nerve toxin.
Accordingly, while known compositions and processes are suitable for their intended purposes, a need remains for improved silicone rubber materials. In addition, a need remains for fuser member layers exhibiting thermal conductivity, hardness, and toughness. Further, there is a need for fuser member silicone rubber layers exhibiting reduced swelling in solvents and silicone oils. Additionally, there is a need for fuser member fluorosilicone rubber layers that are stable at high temperatures. There is also a need for fluorosilicone materials that exhibit improved stability at high temperatures. In addition, there is a need for fluorosilicone materials that emit reduced amounts of undesirable materials such as trifluoropropionaldehyde or formaldehyde at high temperatures. Further, there is a need for fluorosilicone fuser members with improved environmental, health, and safety characteristics.